In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date part of common general knowledge, or known to be relevant to an attempt to solve any problem with which this specification is concerned.
A typical known powered door assembly is illustrated in FIG. 1, which shows a sectional garage door 10 comprising an articulated series of linked panels (in this example, four) arranged to be guided by edge rollers running in lateral guiding and support tracks 12, between a closed vertical position (as shown) and an open, overhead horizontal position.
Remote-controlled operator device 14 comprises an electronically controlled electric motor drive to operate door 10 by way of door arm 16, hingedly connected to door 10. Operator 14 drives door arm 16 by means of a drive spocket engaging with a chain 100 which moves a drive trolley 18 along an overhead longitudinal track 20. Track 20 is mounted by way of a header 22 to the wall above the garage door opening, and an idler sprocket (not shown) is mounted at the header end 22 of track 20. Trolley 18 can therefore be moved in both directions thereby to open and close door 10. An emergency release handle 24 is provided, attached by way of a cord to trolley 18 to allow selective disengagement of the trolley from the chain, in order to manually operate the door in the event of power failure, etc. Chain 100 thus forms a closed loop mounted for travel in a horizontal plane, as shown in FIG. 1A, which illustrates the use of a C-section track or channel 20 partially enclosing the chain and configured to support and guide trolley 18.
Chain 100 is supported by the drive and idler sprocket with which it engages, and a degree of sag in the chain is unavoidable. Consequently, and particularly during acceleration and deceleration, chain 100 has a tendency to come into contact with the walls 30 of the longitudinal track 20. Both track 20 and chain 100 are metallic and therefore a significant amount of noise and vibration can be generated when contact occurs. In alternative assemblies, employing a central longitudinal metal rail (in place of a partially closed track) along which the trolley runs, the chain can come into contact with the sides of the rail, also giving rise to noise and vibration problems.
Such chain noise can be unacceptable in some residential installations, particularly if close to adjoining bedrooms, living rooms, etc. Door manufacturers have in the past accordingly attempted to minimise the occurrence of noise in a number of ways. Toothed rubber drive belts can be used in place of metal chains, which are significantly quieter in operation. However, such belts are generally considerably more expensive than chains, and this solution is therefore not appropriate in all situations.
US patent application Ser. No. 2007/0283627 proposes the use of vibration damping pads for use between a garage wall adjacent the garage door and a track support, which can assist in reducing the transfer of vibration and noise to the building itself However, this approach does not tackle the problem of the generation of noise.
Some manufacturers and installers have in the past applied adhesive noise reduction pads at regularly spaced positions along the inner walls of the track. The pads can assist in minimising the risk of metal-to-metal contact and thus reducing the noise generated. However, this solution has also not been wholly successful, as such pads can be worn down or worn off over time. Moreover, it can be difficult to access the interior wall of the rail to install or replace the pads, particularly when the chain is in place.
The present invention sets out to achieve an improved, or at least an alternative, solution to this problem.